How do you guys do greedy?

I was solving few of the questions under greedy section. It seems kind of a very impossible situation to think in right way towards solution while solving greedy questions. Take example of question 581, i had applied multiple solutions but the was never in line with working solution. Only i remember the solution in future, i can solve this question. They all seem to have different solution to every different question which i guess you can’t solve on the spot. Is it me or anyone else feels the same?